US2973459A

US2973459A - Compensator relaying assembly

Info

Publication number: US2973459A
Application number: US685155A
Authority: US
Inventors: William K Sonnemann
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1957-09-20
Filing date: 1957-09-20
Publication date: 1961-02-28
Anticipated expiration: 1978-02-28
Also published as: CA633630A; JPS357613B1; FR1210966A; GB858638A

Description

Feb. 28, 1961 4 Sheets-Sheet 1 Filed Sept. 20, 1957 UZON OX b- 1 w. K. SONNEMANN 2,973,459

COMPENSATOR RELAYING ASSEMBLY 4 Sheets-Sheet 2 Filed Sept. 20, 1957 L 5% iii Feb. 28, 1961 w. K. SONNEMANN 2,973,459

COMPENSATOR RELAYING ASSEMBLY Filed Sept. 20, 1957 4 Sheets-Sheet 4 CT II BC FAULT NEAR BB 0 52 BI b Fig.6.

D -a F|g.3- M 525355 Fig.8.

UflitdSW i s 1,973,459 7 v I ,COMPENSATORRELQYING ASSEMBLY l Ka sonne manm Roselle Park, N.J., assigno'fto- Pa., a corporation of Pennsylvania V Filed Sept. 26, 1957, Ser.No. 685,'155 f .I V '27 C1. 31747 -My invention relates to a protective relaying system which uses polyphase-responsive elements energized'from one or more of the line-currents, for deriving a set of compensated three-phase relaying voltages which reproduce some aspect of the line-voltages at sme-predetereral .types just described, in which the polyphase-responsive element is a multipolar torque-producing element using a cylindrical rotor, the multipolar element preferably having four poles which are so energized as to produce two diametrically flowing fluxes, each flux being responsive to one of the two compensated voltages wesfinghbusenlcmc p m. E Pittsburgh, which-are applied to said torque-producing element.

such a torque-producing element is known to combine the advantages of a high operating-torque, and a low inertia, which together spell a high rate of response and great sensitivity of response, in combination with the elimination of the objectionable double-frequency pulsating torques .Since sucha two-flux torque-producing element is not a balanced three-phase element, its energizing connections should be such asvto provide no flow of zero-sequence current in the torque-producing element,

. so as to. eliminate hybrid torques which are responsive of the element.

mined fault-locationin the power-line or system, in

combination with polyphase-responsive relaying-means, energized from said compensated polyphase relaying voltages, for developing an operating component which is; responsive to the magnitude of the negative-sequence component of said compensated "three-phase relaying voltages, and a'restraining component which is-similarly responsive to the magnitude of the positive-sequence component of said compensated relaying voltages; or the relaying means may operate on the principle of a polyphase induction motor, energized from said compensated three-phase relaying voltages; or the relaying means may operate on theprinciple of a sine relay, energized from' two of the phases of said compensated three-phase relaying voltages, forv operating in response to the product of the magnitudes of said two-phases, multiplied byfthe sine of the phase-angle between them.- t My invention also relates to;the-combination of a phase-fault relaying meansfor responding" to both grounded and ungrounded double-linefaults LLG and LL, and a three-phase relaying means 3 5, for responding to three-phase line-faults, characterized by at least one of said relaying means being a polyphase-responsive relay which ,isenergized from :c'ompens'at'ed voltages'as above-de's'cribedi'l This full 'protects', thepower-line against all kinds of multiple-conductor vfaults, orfaults involving more than one of the line-conductors of the power-line. That is, my relaying. asser'nbly,-as aw-hole, protects the power-line against all types of faults except single line-to-ground faults LG, which will'have to be taken care of byconventional protection isneeded.

More specifically, my invention also relates to a com pensator'phase fault relay 'in which a polyphase-responsive element is energized from the three-phase bus voltages, each phase 'offiwhichis compensated by, in

ground-relays when such 1;;

My invention has many advantages, including a great reduction in the number of relaying elements which are necessary for the protection of the power-line in each of the three distance-zones, zone 1, zone 2 and zone 3, which are commonly used in distance-relaying. Since the torque-producing element responds to phase-sequence components, a separate element is. not needed for each phase. My invention also has an advantage resulting from the fact.that the polyphase-responsive compensatedvoltage distance-responsive relaying-elements are inherent- 1y directional, thereby avoiding the need for a separate directional element or means, and eliminating the contact-coordination problem which is entailed by the use :ofseparate distance and directional elements. This inherent directional response is obtained both at the balance-points of the distance-responsive elements andat the relaying bus, or more exactly, at the location of the linecurrent transformers.

'In all types of compensated-voltage distance-relays usingthe general principles of my invention, the relayresponse is zero if the fault is located exactly at the balance-point of the relay; if the fault is nearer than the balance-point, the negative-sequence component: of the impressed relay-voltage is larger than the positive-sequenc'etcomponent, and the relay produces response in the operating direction; but if the fault is beyond the balance-point, the positive-sequence component is the larger, and the relay-response is in the restraining direction. .But since the polyphase-responsive relaying element is very sensitive to small positive and negative-sequence components, the balance point can be set very accurately, much more accurately than has heretofore been achieved.

'In the case of faults which are located close to the relaying bus, or, more exactly, close to the line-current transformers, it will be noted that the compensatorvoltage will'be in one direction if the fault is in front pensatorsbeing similar-to eachother, and being respectively connected betweenthe corresponding phases of the o e a t e co resp nd g phases otthc ment.

Still more specifically, 1m y invention relates to compensated-voltage, relaying and systems of the genlocation which is immediately in front of the line-current transformers, so that the relay-operating response is a maximum at this fault-location; but if the fault is located immediately back of the current-transformers, the com- 3 pensator-voltages will add to the bus-voltages, making the positive-sequence relay-voltage component always much larger than the negative-sequence component, and the relay-response will suddenly be reversed, so zthat'there will be no relay tripping response.

In the case of other compensated'relays, such as'threephase relays 3which use the general ideaof subtracting one or more compensator-voltages from the bus-voltages, but not me balanced fashion as inmy phase-fault relay the compensation of .the .threeephase :relay 34 may be such that the relay-response is zero for a three-phase fault which is located very close to the line-currentztransformer at the relayingstation, andthenegative sequence component of the relaying voltagewillprevailtfor faults located a very little way in :front of the current-transformers, while the positive-sequence component will :pre-

a manac" a it r vail 'for faults located a very little way back of the current-transformers.

With t-heforegoingand other objects in view, my.'in-

vention consists in the apparatus, circuits, combinations ing myinvention in the relaying equipment which isrp'rovided at one relaying terminal ina icomplete carrier current relaying r system for the complete protection of Ca power-system, including protection against ground-faults as wellas all kinds ofphase-faults,

Fig.3 is a diagrammatic detail'of theifirst-zone phasefault element 1, of- Fig. 1, showing the use of a four pole cylinder-type torque-producing element, I

Fig. 4 is a very muchsimplified diagrammatic view showing my phase fault element, ina form. which is useful in explaining some of its basic principles,

Figs. 5, 6 and 7 are vectorsdiagrams-which :willibe referred to in the descriptionofthe operation of Fig. 4, and v Fig. 8 is a very :much simplified diagrammatic-view showing certain-basic principlesoft'he Scott connection of the derived potential-transformervoltages Whichare to be compensated and thentapplied'to my phase fault relay. 1

-In Fig. 1, -I showtmy acompensator relaying system,

.various operating-coils of the respective relays are shown as dotted vertical stems, which are intended as a convention for indicating the mechanical connection between the parts of each relay-element. As a further convention, the same legends are applied, both to the forceproducing or operating-members, and to the contactmembers of each relay-elemenn'to denote their relationship. The timerjID hastwo contacts, which are distinguished as TD2 and TD3, which close after different time-delays suitable for the second-zone and third-zone relays, respectively.

Each of the six illustrated relaying-units operates on compensatedvoltages. Sincethe :amount of the mutual compensator-impedance, which is required in the altermating-current relaying circuits, is directly proportional to the value of the derived bus-voltage which is used in said relaying circuits, 1 have shown, in Fig. 1, a convenient means for aiding in adjusting the effectiveimpedancevalue ,of veach'compensator, by adjusting the value of the derived bus-voltage which is applied to the relaying circuits. To this end, I show a plurality of autotransformers AT, each having three adjustable primary-connection taps numbered 1, 2, and 3 on each main autotransformer-winding S. The secondary or output circuit of eachautotransformer in Fig. 1 is permanently connected tothe tapSl, and this secondary circuit serially includes some fine-adjustment taps on a tertiary winding M of the autotransformer'which can add or subtract small fractional increments to the secondary voltage, according to the polarity of the connections of the M-taps. The output-circuit of the tertiary autotransformer-windingM-produces the effective bus-voltage which is used in that phase .ofzthe relaying circuit.

.In the; preferred form of embodimentof my invention, which is shown. in Fig. 1, eachof thecompensators CF is provided with..atapped primary winding T, haying. a

- small number ofvturns, and; a secondary winding ,15,;having a'largev number" of turns, these two windings being applied for the protection of a lthreeephase line-section In Fig. 1,I show sixirelayin-g-unitswhich I-call type KDunits, twofor each ofvthe three zones of protection, 3

namely, a phase-fault. unit for responding to .allzkinds of double-line faults, and a three-phase .unit 3.. :for responding to three-phase faults, for-each zone, the zones being indicated byappended numbers, such as the designation 1 for the fii'st-zone-phase fault lunitior' element. I also show a time-delay element ortimer TD; ani'auxiliarytimer-starting relay TX, and three contactor-switches CS1, CS2 andCS3. The contacts of thecircuitbreaker CB and-the various relay-elements are shown in their deenergized positions, and are regarded assbeing raised by the-operation of the respective elements. The physical connections between the various relay contacts and- "the" magnetically; interlinkedthrough an air-gapped core '16, so that the compensator-voltage which is generated in the secondary winding 15 will be subs-tanitally or ,less, out of phase with the current which traverses the primary winding -T, depending upon the amount of effective re- .sistance R1. The taps of the primary windingT of :each

compensator-GP are numbered in various ohm-values which are so chosen thata correct replica of the positivesequence line-irnpedanceZ of the protectedline 11, to :a distance as-far as the desired balance-point of the relay, will be obtained'when a where..T, S and-M; are the numbers or fractionalnumbers which are-marked on the chosen taps ofthe compensator: primary-T, the main autotransforrner-winding S, andthe tertiary.autotransformerrwinding M, respectively. In this manner,: I; provide a very convenient means for setting themutual impedance of the compensator to. have an ohmicvalue whichmatches the line-impedance of any given. line fl at; any balance-point distance from the relaying station, at which it is desired for the relayto have .a zero response or abalance-point. While this particular typeof balance-point compensator-adjustment. is. preferred, Lam; of course, not limited altogether thereto. It willbe. subsequently explained that, for the best. re 'sults,the' impedanceangle of the compensatorrimpedance should. match the impedance-angle of. the particular transmission-line 11 which is being protected. 1 In accordance with" an invention which is described and claimed 'inan application of Howard -J.'- Calhoun,--Serial No. 685,167,lfiledSeptember 20, 1957,-"Fig.1 shows a prehferrdway 'toadjust'the phase/angle relation between the primary current of each compensator and its secondary voltage, without usinglarge values of resistance, and without; causing much change in t-heimutual' impedance-cr me output-voltage of the compensator as a result of changes in-the angle-adjustments. To this end, a small percentage of the total number of turns of the secondary winding 15 of each compensator CP are shorted through a variable resistance R1, which can be varied from R1=0, to provide a minimum impedance-angle, to R1 --600 ohms, to provide a maximum impedance-angle of approximately 85 (for example); or the resistance R1 may be infinity, or an'open circuit, to provide an impedance-angle of substantially 90. The combination of a small value of resistance R1 and few shorting turns on the secondary winding 15 not only reducesthe compensator-burden, but it also results in a minimum change in the mutual impedance when the value of the resistance R1 is changed for the purpose of adjusting the compensator for lines of different impedance-angles. This provides the best means which has heretofore been devised for accomplishing this purpose.

Referring, now, to the phase-fault units -1, -2 and -3 of the three zones, 1, 2 and 3, of the non-carrier type KD relaying system shown in Fig. 1, it is a characteristic feature of these units, in accordance with my present invention, that each unit uses three identical compensators CP, connected in series with the respective open-delta voltage-terminals V V and V which are supplied by two autotransformers AT. One of these two autotransformers AT has-itsprimary connection across the delta phase ha of the potential-transformer bus abc, while the other autotransfor'mer has its primary connection across the delta phase be. The three phase-fault relay-units 1, -2 and -3, are designed to respond to line-to- ---line faults and to double line-to-ground faults. Said units are all alike, except for their different. distance-settings, or the different impedance-settings of their compensators CP, as indicated by the choice of the S-taps 1,2 and 3, respectively, for the first, second and third zones, as shown in Fig. 1.

' The output-circuits of the two autotransformers AT of each phase-fault relay-unit, such as the unit -1, thus provide an adjustable three-phase derived bus-voltage V V V The primary windings T of the three compensators CP of each of these phase-fault units, such as -1, are energized from the respective derived linecurrents I ,-I and I which are supplied by the linecurrent transformers CT. The three compensators CP subtract their respective compensator-voltages from the corresponding phases of the derived bus-voltages V V and V producing a three-phase compensated voltage at the points x',-y' and z, as shown for the relay-unit -1in'Fig. 1.

In accordance with my present invention, the compensated voltages x, y and z of each phase-fault relayingunit, such as -1 in Fig. 1, are used to energize a suitable type of torque-producing relaying element which produces no torque at all (that is, it has a balance-point) when the positive and negative-sequence components of the impressed three-phase voltages x, y, z are equal to each other, (which is the case when the voltage-triangle has collapsed to a single line or phase), or when said voltage-triangle has completely collapsed to a point.

.Said torque-producing relay-element has an actuating torque when the negative-sequence voltage-component predominates, while it has a restraining or non-actuating torque when the positive-sequence component predominates. Any .suitable torque-producing element which answers this basic description will sufiice, whether it is a balanced element, like a three-phase induction motor, in which the internal impedances and angular spacings of the element are alike in each phase, or whether said torque-producing element is-an unbalanced .element, such as a two-circuit element, the'two circuits of which are energized from difierent voltages derived from' the impressed three-phase voltages x, y, 2'.

There are advantages in using a two-circuit torqueproducing element, as diagrammatically indicated by the watt-meter type of single-phase relay-element W in each of the six relaying units -1, 3-1, -2, 3-2, -3 and 33 as diagrammatically indicated in Fig. 1. There are various ways in which the two circuits for each of these torque-producing elements maybe energized, from any two differing voltages which may be derived from different phases of the three-phase compensated voltages such as x, y, z of Fig. 1.

In the particular circuit-connections which areshown for -1 relay-unit in Fig. l, the two-circuit torqueproducing element W has one winding-circuit xy en'- ergized across the delta-phase x'y of the compensated three-phase voltages x'y'z', while its other winding-circuit zy' is energized across the delta-voltage phase z'y'. If the circuit-connections to and within the two-circuit torque-producing element W are such that no zero-sequence currents can flow in this element, as in the connections shown for the 1 unit in Fig. 1, then the torque-producing element will. have no hybrid, balancepoint-shifting responses to the product of the zero and positive-sequence relay-currents or to the product of the zero and negative-sequence relay-currents.

As described and claimed in the aforesaid Calhoun application, it is desirable, for best operation, in the phase-fault units, such as -1 of Fig. l, to balance both the steady-state and the transient impedance-angles in the three circuits leading up to the common connection y of the wattmeter-element terminals xy'z. This refers to the impedances'which are connected between the busvoltage terminal a and the relay-terminal y, the impedances which are connected between the buS-voltageterminal b and the relay-terminal y, and the impedanceslwhich are connected between the bus-voltageterminal c and the relay-terminal y. p i q As described and claimed in the aforesaid Calhoun application, the impedance-angles in these three circuits are kept substantially equal, notwithstanding the angle changes which are introduced by changing the primary taps S1, S2 and S3 on the au-totransformers AT, by'iritroducing a resistance R2 in circuit between the points y and y, and providing this resistance R2 with three taps, also numbered 1, 2 and 3, which are changed simultaneously with the S-taps of the autotransformers. Dissimilar transient effects, due to sudden bus-voltage changes in the three circuits ay, by and cy, are compensated for by serially including capacitors C and C, be tween the points x and x and between the points z and z, respectively, to compensate for the inductive reactances in these circuits. The effective values of these angleadjustment capacitors C and C are adjustable by means of parallel-connected adjustable resistances R and R respectively.

These transient-suppressing circuit-portions (C R R2 and (C R balance the phase-angles of the impedances of the three circuits ay, by and cy, with open primaries on the three compensators CP. Thus, when a close-in phase-to-phase fault occurs, behind the current transformers CT, one of the delta bus-voltages V V or V is collapsed to zero. If we assume the extreme system-condition of no back-feed current over the line which is being protected, the compensators do nothing to alter this collapsed voltage. Under this condition, there should be no spurious torque in the relay to cause it to respond incorrectly. These transient-suppressing elements prevent such spurious response as might otherwise be occasioned by the sudden change in the bus-voltages in the extreme case in which there may be no current in the primaries of the compensators.

Fig. 1 also shows three three-phase fault-responsive relays 31, 3-2 and 33, one for each of the three zones. These particular relays embody the basic concept of an invention of S; L. Goldsborough, as described and claimed in his application Serial No. 685,168, filed September 20, 1957. These three three-phase relays are all alik e cept rthc r. dist nce-settings hich are 7 changed in much the same manner as has been described for the phase-fault relays pp-1, 2, '-'3, so that a description of one, say the three-phase element 31, will suflic'e for all.

A principal characteristic feature of this three-phase fault-responsive relay Zip-1, as distinguished from the phase-to-phase fault-responsive relay 1, is that the three-phase relay 3-1 uses only a single compensator CP, which has 1.5 times the efiective mutual impedance of each of the three compensators C-P which are usedin the phase-fault relay 1. The phase in which this single compensator CP is connected, in the relay umt 3-1 of Fig. 1, is designated as phase A. This threephase unit 3-1 uses a single auto-transformer AT, which is similar to the antotransformers which have been described for the phase-fault relay -1. This single autotransformer AT is connected between the phases b and a of the relayi-g bus abs, so as to provide the adjustable voltage V which is phase A of the three-phase busvoltages whcih are used for energizing the torque-producing element W or this three-phase unit 3'1,- the other two bus-voltage phases being the phases b and c, un-

changed.

In the three-phase unit 3 1, the single compensator CP has its secondary winding 15, with some of its turns shorted through a mutual impedance angle-controlling resistor R1, connected in series with the bus-voltage terrni nal V to produce the compensated voltage x, as described for the phase-fault relay ere-1, remembering that the compensator CP in the" three-phase relay 3- 1 has an impedance-setting which is 1.5 times as high as in the phase-fault relay 1,-

'In the case of the three phase relay 3=1 which is shown in Fig. l, the compensator-primary T is traversed by the current -=-(I +I), which is equal to (I -31 Where I is the zero-sequence component of the line-current, as derived by the current-transformers CT, as described and claimed in an application of J. G. Chevalier, Serial No. 685,277, filed September 20, 1957.

- The cylinder-unit W, which is used in the three-phase relay-element 3-1 in Fig. 1, is basically a two-phase induction motor which produces torque in a direction which is determined by the phase-angle between the two voltages, and in a magnitude which is responsive to the product of the two voltages which are impressed upon the torque-producing element. When a three-phase fault occurs close to the bus 12 at the relaying terminal of the protected line 11, all of the delta voltages of the bus will collapse to zero. And since the three-ph ase element 3 6-1 uses only one compensator C'P, there will be a voltage x in only one phase of the three-phase voltages which are supplied to the torque-producing cylinder-unit W, this phase being the phase which contains the Com pens-ator CP. This provides energization for the phasewinding xy of the torque-element W. However, the encrgization forthe other phase-winding zy of the torqueelement collapses to zero, in response to a three-phase line-fault near the bus, which means that the torque-element, if it responded at all under such conditions, would have only a momentary transient response, as a result of its memory-action as the uncompensated zy voltage is collapsing to zero.

In order that the three-phase fault-responsive unit- 3'-1 may react, with accuracy or intelligence, to a threephase line-fault close to the relaying station 12, it is desirable not only to sustain a sufficient magnitude of the uncompensated bus-voltagezy which is applied to the torque-producing element, so that there can be a sufi'icient torque to operate the relay, but also to sustain or maintain the proper phase-angle between the two relayvoltages xyand zy, long enough for the relay to reactat all, and to know in which direction to react, because the. relay-torque is determined by the product of the magnitudes of the impressed voltages, multiplied by the sine er the phase-angle between these two voltages:

and an adjustable choke-coil X1, connected in seriesbetween the bus-terminal c and the terminal 2 of thetorque=producing element W. It is necessary that the duration or decrement of the memory-action of this memory=circuit C1, X1 shall be 'sufficiently long to enable the torque-element to produce any torque at all by the end of the time within which said torque-element must accurately respond, but it is also necessary that the tuning of the circuit which includes the memory-circuit C1, X1 shall be substantially equal to the line-frequency of the protected line 11, so that the oscillating current in this tuned circuit will not get much out of phase with the corresponding line-frequency current, during the number of line-frequency cycles during which it is necessary for the torque-element to respond, with a positive torque for faults in front of the relaying Station, or with a negative torque for faults behind the relaying station.

However, the introduction of the capacitor C1 of the memory-circuit, in the relaying unit 3-1 of Fig. 1, necessarily introduces a transient disturbance, which is suppressed or compensated for, in accordance with the Calhoun invention, by connecting a second capacitor C2 between the points x and x, in the compensated-voltage phase x of said torque-element 3-1 of Fig. 1, this second capacitor C2 being shunted by a resistor R2 which not only enhances the effect of the capacitor C2, but also enables said capacitor to suppress transients with as little memory-action as possible.

The relaying. equipment which is shown in Fig. 1 re= quires a timer, such as TD, which is available whenever there is a line-fault involving at least two of the linephases. While I am not limited as to exact details, I prefer to use a single phase timer TD, which receives an energizing current whenever a fault-current is flowing involving at least two of the line-phases. By way of example, I have shown the timer TD as being a motor element M which is energized from a saturable manyturn current-transformer CT-T, which is in turn energized, for example, by the diiference of the linecu'rrents I and I The timer-motor TD is connected in series with the normally open make-contact TX of an auxiliary timerrelay TX. This make-contact TX is bypassed by a resistance R3, which is sufliciently small to avoid substantially open-circuiting the current-transformer CT-'-'T when said contact TX is open, but the resistance R3 is sufiiciently large to prevent the timer TD from operatingwhen said resistance is connected in series with it.

The six fault-responsive elements of Fig. 1 have cor" respondingly numbered make-contacts -1, 31, q5-2, 3-2, =3 and 33, which are used to control certain relaying-circuits which are shown as being energized from a positive direct-current bus The first circuit which is connected to the positive bus in Fig. 1 is a first-zone tripping-circuit which includes the operating-coil of a contactor-switch CS1, then a circuit 17, then the make contact 1 of the first zone phase-fault u'nit -1, then a tripping-circuit 18, which extends up through the trip-coil TC of the c'irciiit breaker CB, and finally through an auxiliary circuit breaker make-contact CBa to a negative bus the circuit-breaker make-contact C'Ba' being closed when the circuit breaker CB it closed, the circuits being illustrated, however,- with all switches and relays open or deenergized. Twobranch=circuits are also provided between the

points

17 and 18 of the first-zone protective-relaying equipment, these two branch-circuits including, respectively, the make-contact 3-1 of the first zone three-phase unit 31 5-1, and the make-contact CS1 of the confactor-s'vvitch The two

circuits

19 and 20 are joined also by a branch-circuit which includes'the make-contact 32 of the second-zonethree-phase unit 32. Consequently, the circuit 20 is energized as a result of the response of either one of the two second-zone units -2 or 3 -2. This circuit20'thus energizes the auxiliary timer-relay TX, which initiates the movement of the timer TD, whenever there is a line-fault which activates either one ofthe second-zone relays. I

The aforesaid circuit 20'is also used to trip the circuit breaker CB at the end of a predetermined time which is determined by the closure of the 'second-zone contact TD2 of the timer TD, which "thereupon energizes the trip-circuit 18 from the circuit 20. The TX coil, either because of its built-in resistance, or because of an externally connected resistance R4, does not draw sufficient current from the circuit 20 to pick up the second contactor-switch CS2, but the trip-coil TC draws a very heavy current as soon as the second-zone timer-contact TD2 closes, thus causing the second contaetor-switch CS2 to pickup and close its make-contact CS2, which completes a circuit-connection between the

circuits

19 and 18,

thus sealing-in the second-zone tripping-response.

' A third relaying-circuit is connected, in Fig. 1, from the positive bus through the operating-coil of a third contactor-switch CS3, then to a circuit 22, then to two branch-circuits, one extending from the circuit 22 through the make-contact -3of the third-zone phasefault unit -3 to a circuit 23, the second branch-circuit for the closure of the second-zone contact TD2 of the timer TD. The third-zone timer-contact TD3 energizes the trip-circuit 18 from the circuit23, and when this happens, the third contactor-switch CS3 is energized,

'pickingup'its make-contact CS3, and closing a circuitconnection between the

conductors

22 and 18.

At the bottom of Fig. 1, the positive bus is shown as being energized, through a battery-switch BS, from the positive terminal of a battery BAT, the negative terminal of which is grounded, to connect with the grounded negative bus My invention is also adaptable for transmission-line protection-systems using carrier-current. Such a carrier system is shown, by way of example, in a preferred form of embodiment,in Figs. 2A and 2B. The equipment shown in Figs. 2A and 2B agrees with Fig. 1 tothe ex- .tent of using the' same circuit breaker CB, current-transformers CT, potential-transformers PT, first and secondzone elements. -'1, 3-1, -2 and 3-2, and timer TD, as in Fig. 1. In addition, the apparatus in Figs. 2A and 2B includes an auxiliary timer-relay TX which is the same as in Fig. 1 except that it has two operatingcoils TX,2 and TX-3, the first coil TX-2 for operating the timer-relayin response to second zone faults involving-;more than a single line-phase, and the second coil ,IXeJ .tsrpp rati s thetimer-relay in response to third zone faults involving more than one line-phase. The system shown in Figs. 2Aand 2B differs from Fig. 1 in including certain different equipment, which will now be described. 1 a s As shown near the middle of Fig. 2A, the neutral wire of the current-transformers CT, which carries the current 31 is shown as energizingthree coils which have previously been known for the purpose of incorporating single-phase ground-fault'protection in a carrier-current system, these three coils being the operating-coil I of a sensitive, carrier-starting, ground-fault relay I the operating-coil I of a somewhat less sensitive (but still very sensitive) ground-fault detector 1 and the current-coil DO-I of a ground-fault directional'element DO. This ground-fault directional element D0 is also provided with a polarizing coil DO-P, which is shown as being energized, through a phase-shifting impedance including a resistorRS and a capacitorCS, from the open-delta secondary circuit of a set 'of' auxiliary potential-transformers APT,which are energized from the relayingvoltage bus abc.

The equipment shown in Fig. 2A also includes an out-of-step relaying-unit KS, of a compensated-voltage typewhich is shown and describedin an application of S. L. Goldsborough and J. G. Chevalier, Serial No. 685,278, filed September 20, 1957. This carrier-starting relay'KS is a three-phase faulteresponsive relay, having a reach or balance-point which is sufficiently farther cut, away from the, relaying station, so that, in the event of a phase-swing of the transmission-system toward an outof-step condition, the outof-step relay KS will pick-up, some three or four cycles (or other convenient time) sooner than the second-zone three-phase fault-responsive element 3-2.

The out-of-step relay KS of Fig. 2A, is somewhat lik the third-zone phase-fault relay -3of Fig. 1, except that one of the three compensators CP is reversed, as indicated at 24 in the connections to the primary winding T. In Fig. 2A, this reversed compensator CP is shown as the one which is connected in series with phase b of the potential-bus abc. If the impedance of this reversed compensator is exactly 0.5 times the impedance of the other two compensators in this relay-unit, the relay will have a zero response to a three-phase fault which occurs precisely at the relaying bus, or more accurately, precisely at the current-transformers CT, and the relay will have a positive response to three-phase faults which occur in front of the bus, and a negative response (which means, no response at all) to three-phase faults which occur behind the bus.

It is usually desirable, however, to make the impedance of the reversed compensator CP more than 0.5 times the impedance of the other two compensators CP in the (or a certain rearwardly reaching distance measured in a direction opposite to the predetermined balance point in the so-called forward reach of the-relay). The rearward reach is dependent upon the amount by which the. impedance of the reversed compensator exceeds 0.5 times the impedance of each of the other two compensators. If the reversed compensator is set for an impedance which is, say, 0.55 times that of either of the other two compensators, the backward reach of this relay-element will be only a small amount, and this is theoretically sufficient. However, in actual practice, a larger amount of backward reach would ordinarily be used. It may be convenient to use a reversed compensator having the same impedance as the two unreversed compensators, in this out-of-step relay KS, in which case,

7 however, the rearward reach will be considerably less 11 Jesponsecircle of'this-relay :far enough-outside of the response-circle of the second-zone three-phase relay 3-2 so that a line-swing-toward an out-of-step conditionpicks up the KS relay, on the outer circle, a sufficientiimeabefore the system-swing reaches theinner circle.

-The forward reach of thisrelay KS, in response'to three-phase faults, is determined solely by the. setting of the-two unreversed. compensators CP. When Ispeak -of three-phase faults, I-refer to line-conditions which look, to the relay, like a three-phase fault,'as in.an outof-step swing, .as is well understood.

In the carrier-current .system of. Figs. ..2A and 2B,

.-the third-zone. relaying elements 3-3'.and qua-3'v which respond to faults involving more than one line-conductor, are connected insuch polarityas toreach back- -.wardly, rather than. forwardly,'in amanner which has looking third-zone three-phase relay-element 3-3'- of Fig. 2A: the adjustable choke coil X1 of the corresponding third-zone forwardly looking element 3 5-3 of Fig; 1

has been omitted in Fig. 2A, as being unnecessary; the

capacitor-shunting resistor R2- has been made adjustable to provide the impedance-angle-matching function which could previously be accomplished by the adjustable choke coil X1; and the stator windings of the torque-element'W ofthe-reversed third-zone three-phase element 3-3' of "Fig; 2A have been modified by the addition of a singleturn current-energized winding 26, which is located so as to provide a flux in the poles which are energized by the uncompensated voltage-phase yz. This current-energized winding 26 is energized by the same current which affords the compensation for the winding xy of this torque-producing element. This current-energized winding 26 enables the backwardly looking three-phase ele- -ment 33' in Fig. 2A to respond to a three-phase fault at the bus, because, under such circumstances, the torqueproducing element has two out-of-phase fluxes, one due to the compensator impedance-drop, and the other due tothe current (I +I or (I -3I This auxiliary current-energized coil or winding 26 has no effect uponthe relay-performance except for faults which are very close to the bus. It is described and claimed in the aforesaid'Goldsborough application Serial No. 685,168.

"The direct-current relaying circuits of the carriercurrent relaying equipment of Figs. 2A and 2B are shown in'Fig. 2B.

At the top of Fig. 23, a battery BAT'is shown as energizing the-positive and negative buses and through a battery-switch BS.

Next, in Fig. 2B, is shown a circuit 27, which extends frornthe positive bus through the operating coil.of.

a contactor-switch CS to a circuit 28,and. thence through the ground-current relay-contact I and the ground-directional relay-contact D0 to a circuit 29, from which point a circuit continues on, through the operatingcoil of a ground-fault contactor-switchCSG, and a resistance' R5, to'the previously mentioned circuit'21 which extends up through the auxiliary make-contact CBwof the circuit breaker CB, and'thence to'the negative bus The serially connected relay-contacts'l andDO are bypassed by a make-contact 30 of the contactor .ing the. CSG relay,but when the receiver-relay contact 31 closes, energizing the tripping-circuit 18, a heavy'current is drawn by the trip coil TC, thus causing the contactorrswitch CSOtopickup. The contactor-switch CSO thereupon picks up, and closes notonly its previously mentioned make-contact 30, but also a'second make-contact 32,'thislast-mentioned make-contact 32 being used to complete a branch-circuit connection between the points '29 and 18.

Next, Fig. 2B shows acircuit 33, which extends from the positive bus through the make-contact KS of the out-of-step relay KS,-and thence through the operating-coil 34 of a delayed auxiliary out-of-step relay OS,

.to aicircuit 35, and thence through a resistance R6 to the previously mentioned conductor 21 which extends to the negative bus through the. circuit-breaker make-contact CBa. The auxiliary out-of-step relay OS is a delayed relay, which is provided with a slug -or short-circuited winding 36 in suchposition as to make this relay a little slow in picking up.

-Reference will next be made, in Fig. 2B, to a circuit 37, which extends from the positive bus through the operating-winding CS1 of the contactor-switch CS1 to a circuit 38, and thence through the-make-contact -1 of the first-zone phase-fault relay -1= to a circuit 39, and thence through a back-contact 40 'ofthe auxiliary -out-of-step relay OS to 'the trip-circuit '18. A branchcircuit also extendsfrom the conductor 38 to-the conductor '39, through the make-contact 31 of'the firstzone three-phase relay 3-1. A third branch-circuit extends from the conductor 38 to'the tripping-circuit 18, through the contactor-switch make-contact CS1.

. Reference will next be made, in Fig. 2B, to a circuit 41, which extends from the positive bus through the operating-coil of the contactor-switch CS2 to a circuit 42. Two parallel branch-circuits extend on, from the conductor 42 to a conductor 43, one of theseibranchcircuits including the contact 2 of the second-zone phase-fault relay 2, while the other branch-circuit includes'the contact 3-2 of the second-zone three-phase relay 3-2. A third branch-circuit extends from the conductor 42 to the tripping-circuit 18,'through-the contactor-switch contact CS2.

The circuit 43 is thus energized in response to any second-zone fault which involves more than one line conductor, that is, when either of the second-zone relays -2 or 3-2 responds. This second-zone fault-responsive circuit 43 has five branching extensions 43-1through 43-5. The circuit 43-1 extends through a back-contact 44 of the auxiliary out-of-step relay OS,- and thence through a forwardly conducting rectifier 45 to'the previously mentioned circuit 35. The'rectifier 45 thus pulls up the potential of the circuit 35 practically to that of the positive bus (j+), thus short-circuiting (and deenergizing) the operating-coil OS, whenever-there is a response of either one ofthe second-zone relays 2 or 3-2.

The branch-circuit43-2 energizes the operating-coil CSP of a phase-fault contactor-switch CSP, in a circuit which extends through a resistance R7 to the previously mentioned circuit 21; the branch-circuit'43-3 extends to the previously mentioned conductor 39 through a'makecontact 46 of the previouslymentioned receiver-relay RR;

the branch-circuit 43- 4 extends through the second-zone operating-coil TX-2 of the auxiliary timer-relay TX, and thence through a resistor R8 to the circuit 21; and the branch-circuit43-5 extends through a back-contact 47 of the auxiliary out-of-step relay OS, and then through the second-zone contact TD'2 of the timer" TD to'the trip-circuit 18.

Fig. 2B next shows a circuit'48, which extends from the positive bus through the operating-coi l of the contactor-switch CS3 to a circuit 49, andthence through the third-zone timer-contact TD-3 to the tripping-circuit 18. A bypassing circuit-connection is alsosup'plied from '13 the conductor 49 to the tripping-circuit 18 through the contactor-switch make-contact CS3.

The next two circuits of Fig. 2B, starting with a circuit 50, incorporate a specific circuitry which is the invention of Herbert W. Lensner. While I am not limited to this particular circuitry, I nevertheless prefer to use it as being superior to other available circuits, and hence I have shown it in the preferred form of embodiment of my carrier-current relaying-equipment.

In Fig. 2B, the circuit 50 extends from the positive bus through a resistor R9 to the third-zone operating-coil TX-3 of the auxiliary timer-relay TX, and thence to a circuit 50'.

Each of the two backwardly looking third-zone elements 3-3 and -3' is provided with a make-break contact-assembly having a single moving contact 51,- which is common to both a make-contact 52 and a break or back-contact 53. The make-contact 52 of the phasefault element -3' is connected between the negative circuit 50' of the auxiliary-timer-relay coil TX-3 and the negative bus The back-contact 53 of this same phase-fault element -3' is connected between a:

circuit 54 and the negative bus The make-contact 52 of the three-phase fault-responsive element 3 -3' is connected between the aforesaid circuit 50 and the circuit 54. In this way, if there is an operation of the backwardly looking third-zone phase-fault relay '-3, it will disconnect the circuit 54 from the negative bus, and it will connect the circuit 50 to the negative bus,

thus energizing the third-zone operating coil TX-3 ofthe auxiliary timer-relay TX, which starts the timer TD. If thebackwardly looking third-zone phase-fault relay -3' does not operate, but if the backwardly looking third-zone three-phase relay Yup-3' operates, then such operation will connect the circuit 50' to the negative bus through the circuit 54 and the back-contact 53 of the phase-fault relay -3', thus again energizing the third-zone operating-coil TX-3 of the auxiliary timerrelay TX.

The next circuit shown in Fig. 2B is a carrier-starting circuit 55, which extendsfrom the positive bus through a resistor R-10 to a carrier-starting circuit 56,

which, if it is not shorted over to the negative bus will energize the positive circuit 56-4 of a carrier-current transmitter XMTR, which is diagrammatically illusformer 57, which is connected to a circuit 58, which extends up through Fig. 2A, to a coupling-capacitor CC which is connected on the line-side of a carrier-frequency trap 59 which is shown as being connected in;

phase C of the protected line 11.

Three branch-circuits 56-1 to 56-3 are shown, whereby the transmission of carrier current by the transmitterf XMTR may be prevented by connecting the circuit 56 over to the negative bus thereby bringing down.

- contactor-switch CSG, so as to make sure that the carrier is off whenever the relays I and D0, in the circuit 282 9, indicate the presence of a ground-fault in a forwardly looking direction, which requires a tripping operation.

The branch circuit 56-3 is connected to the negative bus through a make-contact 61 of the phase-fault contactcr-switch CSP, which responds when there is a .trated as being coupled to a carrier-current auto-tram second-zone fault involving more than one Iine-conduc circuit 63-2 contains a make-contact 66 of the phasefault contactor-switch CSP.

The last circuit 67 in Fig. 2B connects the positive bus through a holding or restraining-coil RRH of the receiver-relay RR, and thence to the positive circuit 68 of a carrier-current receiver RCVR which is diagrammatically shown as being coupled to the carrier-current autotransformer 57.

In all of the relaying-units in which the torque-producingelernent is shown as a two-phase wattmeter-type element W, which is energized from two different voltages of a compensated three-phase voltage-supply xyz, the essential thing about the torque-producing element W is that is shall be a polyphase-responsive element which develops an operating force when its impressed voltages have a negative sequence of phases, or which develops an operating force which is responsive to the magnitude of the negative-sequence component of the compensated three-phase relaying voltages, and a restraining force which is similarly responsive to the magnitude of the positive-sequence component of said compensated relaying voltages; or that the torque-producing element W shall produce an operating torque when the responding to (fi -F where T); and F are the re- "spectivescalar values of the positive and negativesequence-voltages, such a motor being used as a relay to respond to the negative starting-torque, in the direction of rotation of the negative-sequence voltagevector E or that the'torque-producing element W, if it is energized from a system of delta-connected voltages, shall b'e responsive to the area of the delta-triangle and to the order of phase-sequence or succession of the phases in the delta-triangle; or that the torque-producing clement W, if it is a two-phase element, shall develop an operating force which'isresponsive to the product of the magnitudes of the two relay-voltages, multiplied by the sine of the phase-angle between them. Any relaying device, electro-mechanical, static, or otherwise, which will serve to close an electrical circuit sufliciently to trip a circuit breaker whenever the negative-sequence voltage is greater than the positive-sequence voltage, will do the job within the broad concept of the invention.

When the polyphase torque-producing element W is balanced, in all phases of a symmetrical polyphase set of phases, it will not respond to the zero-sequence voltagecomponent, even though such a voltage-component is present in the impressed voltages. When, however, the circuits of the polyphase torque-producing element W are not balanced, it is quite desirable to keep zero-sequence currents out of said element, either by keeping the zero-sequence voltage-component out of the polyphase voltages which are impressed upon the torqueproducipg element, or by making the connections in such It is to be noted, however,"that the four-pole cylinder- .15 a way :that there is no return-path for any flow ofzerosequence current in any phase-windingofthe element;

thus preventing the possibility of a shifting of the balancepoint of the element as a result of hybrid torques involving the product of the zero and positive-sequence components, or the product of the zero and negative-sequence components.

I believe that my invention-has a-very important utility in its applicability to a cylinder-type multipolar relaytwo diametrically flowing fluxes, in accordance with the broad principles described and claimed 'in the Sonnemann Patent 2,380,197, granted July 10,1945, using a lightweight conducting cylinder as the'torque-producing rotor-member. Such an element has the advantage of compactness, an extremely low rotor-inertia and hence. a high speed of response, and freedom from the pulsating double-frequency torques which interfere with the sensitivity of certain other kinds of wattmeter-type relays.

type relay-element'has only two energizingcircuits, whereas,'to serve in my compensator relaying-system, it must be energized from a three-phase compensated bus-voltage, in such a manner as to respond only when the negatorque at a desired balance-point, such a combination has 035 the very distinct advantage of completely avoiding the necessity for using directional relays in responding to faults involving more than one -line-conductor. The positive and negative-sequence components'of-the compensated polyphase relay-voltages are equal, for faults 40 at the balance-point, while the positive-sequence component prevails for faults which are even-very slightly beyond the balance-point, and the negative-sequence component prevails for faults which are even very slightly nearer than the balance-point. Thus the balance-point of such a combination may beset, and maintain, very accurately, more so'than has heretofore been possible. Such a combination also has an advantage in responding tofaults near the relaying-station bus, because the' linecurrents, which energize the compensators, are in one direction when the fault is in front ofthe line-current transformers, and in the other direction when the fault is behind theline-current transformers.

My present invention relates not' only to' the broad,

principle of using one or more line-current-energized' compensators for compensating the polyphase bus-voltages which are to be applied to' a polyphase-responsive torque-producing element, but it has more particular element W, preferably one which has'four poles, with 10 relation to the phase-to-phase fault-responsive elements such as -1, 2, '-3, and -3 in whichthree equal compensators are used, having impedances equivalent to the positive-sequence line-impedance'to the desired balance-point of the relay, forcomp'ensating the three phase relay-elements in combination with other relayelements which respond tothree phase faults, or, in "general, which respond to all faults other than the phase-tophase faults which are responded to by my phase-to phase relay-elementsexcept single line-to-groundfaults which can be responded to by other means.

i Fig. 3 shows a detail of one of-my phase-to-phase' relay-elements, illustrating the first-zone element -1'of representation of-the -1 element in Fig. 1, by diagrammatically showing a detail of the wattmetric, or torque producing; element W.

'In Fig'. 3, this torque-producing element W is diagrammaticallyshown, in its preferred form of embodiment, as a four-polelcylinder-type element, comprising a stationary magnetizable frame 69 having four salient poles P1, P2,P3andP4, carrying windings W1 to W4, respectively. Inside of the four poles there is a lightweight, -rotatably mounted cylinder 70 of aluminum or other conducting material in which eddy currents are induced for producing a rotational torque tending to rotate the cylinder in one direction or the other, accord ing to the predominance of the positive or negative phaseseqtience component of the currents in the windings W1 to W4. Inside of the cylinder 70, there is usually mounted a stationary cylindrical magnetizable member 71 for providing a return-path for the flux from one pole 'to another, thus making the flux as large as possible, and consequently increasing the available torque. Since the relay-element W operates on alternatingcurrent, its stationary magnetizable members 69 and 71 are preferably'of laminated materials, while the cylindrical rotor-element '70 is preferably made of a light-weight non-magnetizable conducting'material. An operating-arm 72 is attached'to the rotorcylinder 70, for actuating the contact-member 1 when the element W responds.

The general basic principles on which my phase-fault element operates are illustrated more simply in Fig. 4,

wherein the torque-producing element W is more diagrammatically indicated. In this figure, the, potential transformers PT reproduce the bus-voltages V V V which are connected to the relay-terminals xyz through three equal impedances Z each of which is a replica of the positive-sequence line-impedance of the powerline 11, out to the desired balance-point of the relay. In Fig. 4, three separate line-current transformers CT areshown, for circulating the three line-currents I 1 and I through the respective impedances Z which are connected in series with the respective bus-voltages V V and V This is an equivalent simple diagrammatic representation of the compensator-connections of my phase-to-phase relays 5 3.

1 The operation of my phase-fault relay of Fig; 4 will be-explained with the aid of the vector-diagrams in Figs. 5, 6 and 7. "Fig. S-shows' an equilateral triangle E E E which represents the balanced three-phase line-voltages or bus-voltages at the relaying stationwhen thereis no fault on the system. The delta line-voltages are shown as the sides of the triangle, as indicated by the arrows E E and-E 1 In any problem-dealing withline- '-impedances,- it'must be remembered that the line-impedances are the impedances of individual line-wires, and hence they are line-to-neutral impedances, and not delta impedances. In like manner, the line-currents I 1 and .I towhich reference has been made,'in other figures, are 'line-to-neutral orstar-currents. Therefore, in any prob- 1cm in which line-impedances are involv'ed,-and specifically "in connection with my compensator relaying system in which line-current-energized compensators are involv ed; it-is necessary to use, in the calculations, the line- -to'neutra1 or star voltages as indicated in Fig. 5 at'NE NE and NE My phase-fault relay, as basically shown in Fig. 4, is

desigried -to -respond"'when the negative-sequence component 'of the compensated bus-voltages xyzis larger than the positive-sequence component.

The voltage-drops in the compensator-impedances Z of Fig. 4 are subtracted from the'line-to-neutral bus-voltages V V and V of 'the relaying circuits,-which may be regarded as reflecting the line-to-neutral voltages E,,, E, and E of the actual -line 11, or bus 12, which are shown in Figs. 5 and 6.

Since my phase-fault relay, with three identical comgy y of p e- "'F g- 3Wdiffers from"the pei1sators, develops an Operating torque only in response 'to'thefnegative-sequence component of the compensated voltages xyz, this relay does not respond to three-phase faults which do not-have any negative-sequence currentcomponents. My phase-fault relay is intended to respond to faults involving any pair of the line-conductors A, B and C, whether the faults involve ground-currents or not.

Since the compensator-connections are balanced, that is, the same in each phase, it is possible to adopt the usual convention, which is usual in non-compensated cases, of denominating the faulted phases as B and C, in a line-to-line fault.

When a BC fault occurs on the power-line 11, if the fault is ungrounded, as is commonly indicated by the designation BC, ,it will collapse the delta-line-voltage E practically to zero, at the fault. At the relaying station, as indicated in Fig. 6, the delta bus-voltage E or (E -E Will be only partially collapsed, depending upon the line-drops due to the line-currents flowing in the faulted-phases B and C. There will also be a voltage-triangle distortion at the bus, resulting in a shortening and a phase-shifting of the delta bus-voltage E as shown in Fig. 6, due to the flow of the unbalanced faultcurrent in the source-impedance back of the bus.

If a BC fault occurs exactly at the balance-point of my phase-fault relay, it will be noted that the voltagedrops in my compensators in phases B and C will exactly match the voltage-drops in the line-impedances in these two phases, up to the point of'fault. As shown in Fig.

'6, the compensatorsin phases B and C will substract,

from the bus-voltages E, and E respectively, the compensator-drops (E B2) and (B C2), where the points B2 and C2 coincide with the mid-point D in the line EBE If the BC fault in Fig. 6 should be further away than the desired balance-point of the relay, the portion of the fault-current which is supplied from the relay-station bus 12 will be smaller, because of the greater line-impedance up to this more distant fault-location, and hence the linecurrents will be smaller, in the faulted phases B and C, and the voltage-triangle of the compensated voltages xyz which are impressed upon the torque-producing element will not be collapsed to a straight line E D, but will be a positive-sequence triangle (E5, B1, C1). Thus, the torque-producing element will be energized with a threephase voltage having the positive phase-sequence, and

hence the element will not respond.

If, however, the BC fault 'in Fig. 6 should be closer than the balance-point of the phase-fault element M: of Fig. 4, the line-currents which are supplied by the current transformers CT of Fig. 4 will be larger than they would be for a fault atthe balance-point, and hence the voltage drops (E B3) and (B C3), in Fig. 6, will extend beyond the median point D, resulting in a negativesequence relay-voltage triangle (E,,, C3, B3), in which the negative-sequence succession of phases prevails, and hence the relay will respond to all faults which areeven a tiny bit closer to the relaying station than the balance-point of the relay. It is to be observed that this discrimination between line-to-line faults which are at or beyond the balance-point, and line-to-line faults which are closer than the balance-point, is obtained by a single relay, regardless of the pair of line-phases wich are involved in the fault.

Fig. 7 shows how my phase-fault relay 3 of Fig. 4 responds to aBC fault which is either at the bus or very close to the bus (i'n front of the bus or behind the bus).

When a BC fault occurs at'or very close to the bus, the delta bus-voltage V will collapse essentially to a single point D, as shown in Fig. 7, so that the voltage-triangle at the bus at the relaying station will become a single line E D, representing a single-phase voltage. If such a voltage were applied to a polyhpase-responsive torqueproducing element, without any compensator-action, the element would fail to respond. In my-cornpensator relaying system, however, the phase-fault elementpp' of Fig.

18 4 uses compensators which are the same in all three phases, so that the torque-producing element will be energized from an uncollapsed three-phase compensated-voltage triangle. It makes a difference whether the faultcurrents are positive or negative. If the fault is in front of the current-transformer CT, the fault-currents which are supplied to the compensators may be regarded as positive; but if the fault is behind the current-transformers, the line-currents which are supplied by the current transformers will be reversed, and can be regarded as negative currents.

Thus, in Fig. 7, if the compensators receive positive currents, for a BC fault immediately in front of the current transformers CT of Fig. 4, the voltage-drop in the compensator in phase B will be (D, +B). In like manner, the compensator in phase C, when receiving a positive current, for a BC fault immediately in front of the current transformers CT of Fig. 4, will produce, in Fig. 7, a compensator-voltage (D, +C). Thus, for a BC fault immediately in front of the bus (or more exactly, immediately in front of the current transformers CT), the compensated three-phase voltages which are used to energize the torque-producing element of my phasefault relay will have a negative phase-sequence, such as (E,,, +C, +B) in Fig. 7, and the torque-element will accordingly respond strongly. If, however, the BC fault had been behind the bus (or, more properly, back of the current-transformers CT), the compensator-drops or voltages will be reversed, as indicated by the minus signs in Fig. 7, and the compensated three-phase voltages xyz which are used to excite the torque-element will have a positive phase-sequence, or succession of phases, as indicated at (E,, B, -C), and the torque-producing element will be pressed tightly back against its back-stop.

Thus, it will be seen that my compensated-voltage phase-fault relay is inherently directional in its action, discriminating between faults which are in front of the bus, and those which are behind the bus. Consequently, there is no need for an additional directional element or means, such as has been used'in previous protective=relay systems. I have eliminated, therefore, not only the cost of the wiring-circuit complication of a separate directional element, but also the contact-coordination problem which has heretofore been entailed by the use of separate distance and directional elements.

In the previous illustrations, I have shown a two-phase torque-element which is energized across two open-delta phases of the compensated three-phase voltage xyz, with the explanation that the torque-element could have been a balanced three-phase motor-element of any kind, or that it could have been a two-phase element which is energized from any two diverse voltages which are extracted, in any "way, from the compensated bus-voltages.

The two-circuit, four-pole, cylinder-type torque-element W, which is shown in Fig. 3, is sometimes a little hard to adjust properly, when energized from two open-delta phases of the compensated three-phase voltage xyz. This situation may sometimes be alleviated by using a Scottconnection of either the autotransforrners AT, or .the torque-element W, or both.

In Fig. 8, an alternative illustration is given, showing the use of the Scott-connection on the autotransformers AT, while using an ordinary two-circuit wattmeter type of torque-producing element W. Thus, in Fig. 8, an autotransformer BC, having a mid-tap O, is connected between the line-phases B and C; while another autotransformer A0, having a tapped point A which is of the distance up from the point 0, is connected between the line-phase A and said point 0. Three identical impedances 2 corresponding to the line-impedances up to the desired'balance-point, are connected, respectively, be tween the points A and x, between the points B and y,

and between the points C and z, and these impedances Fig. 8 is connected between the points z and y while the other circuit of said torque-element W is connected ,between the points x and O. This constitutes another way in which a two-circuit torque-element W maybe energized in a satisfactory manner, from a compensated threephase voltage-supply. In this Fig. 8, it will be noted that the autotransformer voltages BC and AO, which are used in energizing the two winding-circuits of the wattmeter or sine-type relay W, are 90 out of phase with each other, under normal conditions of balanced three-phase voltages. This tends to produce a maximum torque in a sine-type relay.

In the foregoing forms of embodiment of a relaying assembly including my invention, I have shown and described certain mutual compensator-impedances which match the line-impedance of the protected power-line 11, to a predetermined point which is to correspond to the balance-point of the fault-responsive relay in question; or in some cases, I have defined the compensator-impedance as being the equivalent of a certain multiplier times the balance-point line-impedance Z The balancepoint line-impedance Z to which I have been referring, includes the small resistance-component of the line-impedance, as well as the large reactive component thereof. This is shown by the provision of the resistance R1 (Fig. 1), which causes the phase-angle of the efiective mutual compensator-impedance to match the phase-angle of the line-impedance of the particular power-line 11 which is being protected. The reason for this, is that I am using compensated bus-voltages. I am using a linedrop compensator or compensators to produce either the same proportionate voltage-drop as would be obtained in the line itself between the bus and the desired balancepoint of the relay, or in other cases I have used a compensator voltage-drop which is related, in certain other defined ways, to the voltage-drop in the line-impedance between the bus and the aforesaid balance-point. By causing the compensator-impedance to have the same phase-angle as the line-impedance, and by energizing .the compensator with the same line-current which cause-s the impedance voltage-drop in the line, I achieve the result that the compensator voltage-drop will always lie along the line of the line-drop voltage from which the compensator-voltage is subtracted, or to whichthe compensator-voltage is added, depending uponthe polarity of the compensator-connections. While theoretically, some .sort of possibly tolerable accuracy of response might be obtained by ignoring the resistance parts of the line-impedances, the generator-impedances, and the like (as has been done with previous types of distance-responsive relays which did not use compensated voltages in the .manner WhlCh I am doing, in responding to faults), I

believe that the additional accuracy of operation which is obtainable by matching the phase-angle as well as the magnitude or magnitude-ratio of the line-impedance to the balance-point, is sufficiently important to more than warrant the slight additional complication which is involved by the use of the resistor R1 or its equivalent.

In the preceding description of the fault-responsive units, such as the phase-to-phase unit -1 in Fig. l, I

have stated that the effective impedance of certain com- ;pensators is equal to the line-impedance to a fault at the of a well-constructed balanced transmission-line in which there is adequate transposition of the phase-wires. In the case of a non-transposed transmission-line, the reactance parts of the impedances of the three line-wires will not all be the same, and it must be understood, in such a case,

that each such-compensator could be set to match the impedance of its own line-wire; I wish my description to be read with this explanation in mind.

Inthe preceding description of the coincidenceofthe phase-angle of the compensator voltage-drop with' thei' 'o phaseangle of thevoltage to which the compensator voltage-drop is beingadded or subtracted, I have really been assuming thegeneral case in which the impedance of the fault itself is negligibly small, so that'the voltage between the faulted phases is zero at the fault.

While I have illustrated my invention in several different forms of embodiment, and while I have explained the general principles of its design and operation in the best form and manner at present visualized, I wish it to be understood that the foregoing illustration, description and explanations are only by way of example, and were not intended as limitations, in the sense that it is possible to substitute various equivalents, or to add certain additional refinements, or to omit certain of the illustrated refinements which may not be needed inany particular case, without departing from the essential spirit of my invention.

I claim as my invention:

1. A compensator relaying assembly, for protecting a three-phase transmission-line against certainkinds and locations oftaults, comprising: a means energized from the line-voltage at the relaying station, for producing a setof derived polyphase voltages having a phase-sequence corresponding to theline-voltages; a compensating-means, including a compensator connected in series with a phase of said derived polyphase voltages for producing a set of compensated polyphase voltages; a means for energizing said compensator proportionately to the line-current which flows in a line-conductor of the three-phase transmissionline; and a polyphase-responsive relaying element, ener gized from said compensated polyphase voltages, for con trolling an electrical circuit when the compensated volt ages-have a-negative sequence of phases, said compensator comprising an inductive reactance element having a ferromagnetic core provided with an airgap.

2. A protective-relaying combination for responding to certain faults on a three-phase transmission-line, includ ing: a means, energized from the line-voltage at the relayingstation, for producing a set of derived polyphase voltages for relaying purposes; a compensating-means, including a compensator connected in series with a phase of said derived polyphase voltages for producing a set of compensated polyphase voltages; a'means for energizing said compensator proportionately to the line-current which flows in a line-conductor of the three-phase transmission.-

line; and a polyphase-responsive relaying element, energized from said compensated polyphase voltages; said compensator having substantially the same impedance- 'angle as the line-impedance of said three-phase transmission-line, and having an impedance-magnitude which is so related to theline-impedance to a predetermined fault-location, as to cause said-relaying element to have a balance-point when ajjpredetermined'type of fault occurs at said predetermined fault-locatiomwhereby said element will respond to nearer faults of said type, but will not respond to more distant faultsof said type.

'3. A protective-relaying combination for responding to certain faults on a three-phase transmission-line including: a means, energized from the line-voltage at the relaying station, for producing a derived polyphase voltage for relaying purposes; a line-drop compensating-means, connected' in series-circuit relation'to'said derived polyphase voltage, for reproducing some aspect of the three-phase line-voltage at some predetermined fault-location in the transmission line, whereby to produce a polyphase compensated relaying voltage, which collapses to a single phase when a predetermined type of fault occurs at said predetermined 'fault-locatiomwhich has the same positive s'equ'ence of phases as the transmission-line when said predetermined'type of fault occurs at a point beyond said "predeterminedfaultdocation; and which has a negatve sequenceiof phases whensaid predetermined type of fault occurs. at ,a'poi'nt nearer than said predetermined fault-locationjq-anda polyphase responsive relaying ele- .ment, euergiz edironr said polyphasecpmpensated V relaying voltage, for controlling an electrical circuit when the phase when a predetermined type of fault occurs at said predetermined fault-location, which has the same positive sequence of phases as the transmission-line when said predetermined type of fault occurs at a point beyond said predetermined fault-location, and which has a negative sequence of phases when said predetermined type of fault occurs at a point nearer than said predetermined faultlocation; and a polyphase-responsive relaying element, energized from said polyphase compensated relaying voltage, for controlling an electrical circuit when the polyphase compensated relaying voltage has a negative sequence of phases, the circuit-connections of said polyphase-responsive relaying element being such that said element does not respond to any zero-sequence component of the polyphase compensated voltage.

5. A protective-relaying combination for responding to certain faults on a three-phase transmission-line, including: a means, energized from the line-voltage at the relaying station, for producing a derived polyphase voltage for relaying purposes; a line-drop compensating-means, connected in series-circuit relation to said derived polyphase voltage, for reproducing some aspect of the threephase line-voltage at some predetermined fault-location in the transmission-line, whereby to produce a polyphase compensated relaying voltage, which collapses to a single phase when a predetermined type of fault occurs at said predetermined fault-location, which has the same positive sequence of phases as the transmission-line when said predetermined type of fault occurs at a point beyond said predetermined fault-location, and which has a negative sequence of phases when said predetermined type of fault occurs at a point nearer than said predetermined faultlocation; and a torque-producing relaying element having a polyphase stationary element which is energized from said polyphase compensated relaying voltage, and having a lightweight cylindrical rotor element of conducting material, carrying a contact which is moved in a responsive direction when the polyphase compensated relaying voltage has a negative sequence of phases.

6. A protective-relaying combination for responding to certain faults on a three-phase transmission-line, including: a means, energized from the line-voltage at the relaying station, for producing a derived polyphase voltage for relayingpurposes; a line-drop compensating-means, connected in series-circuit relation to said derived polyphase voltage, for reproducing some aspect of the threephase line-voltage at some predetermined fault-location in the transmission-line, whereby to produce a polyphase compensated relaying voltage, which collapses to a single phase when a predetermined type of fault occurs at said predetermined fault-location, which has the same positivesequence of phases as the transmission-line when said predetermined type of fault occurs at a point beyond said predetermined fault-location, and whichhas a negative sequence of phases when said predetermined type of fault occurs at a pointnearer than said predetermined faultlocation; and a polyphase-responsive torque-producing relaying element having a four-pole stationary element having windings energized from said polyphase compensated relaying voltage for producing two diametrically flowing a contact which is moved in a responsive direction when the polyphase compensated relaying voltage has a negative sequence of phases.

7. A protective-relaying combination for responding to certain faults on a three-phase transmission-line, including: a means, energized from the line-voltage at the relaying station, for producing a set of derived polyphase voltages having a phase-sequence corresponding to the line-voltages; a compensating-means, including a compensator connected in series with one of said derived voltages, and having substantially the same impedance-angle as the line-impedance of said three-phase transmission-line, for producing a set of compensated polyphase voltages; a means for energizing said compensator proportionately to the line-current which flows in the corresponding lineconductor of the three-phase transmission-line; and a polyphase-responsive relaying element, energized from said compensated polyphase voltages.

8. A protective-relaying combination for responding to certain faults on a three-phase transmission-line, including: a means, energized from the line-voltage at the reiaying station, for producing a set of derived polyphase voltages having a phase-sequence corresponding to the line-voltages; a compensating-means, including a compensator connected in series with one of said derived voltages, and having substantially the same impedanceangle as the line-impedance of said three-phase transmismission-line, for producing a set of compensated polyphase voltages; a means for energizing said compensator proportionately to the line-current which flows in the corresponding line-conductor of the three-phase transmission-line; and a two-circuit polyphase-responsive relaying element, energized from said compensated polyphase voltages.

9. A protective-relaying combination for responding to certain faults on a three-phase transmission-line, including: a means, energized from the line-voltage at the relaying station, for producing a set of derived polyphase voltages having a phase-sequence corresponding to the line-voltages; a compensating-means, including a compensator connected in series with one of said derived voltages, and having substantially the same impedance-angle as the line-impedance of said three-phase transmissionline, for producing a set of compensated polyphase voltages; a means for energizing said compensator proportionately to the line-current which flows in the corresponding line-conductor of the three-phase transmission-line; and a two-circuit polyphase-responsive relaying element, energized from said compensated polyphase voltages, the circuit-connections of said polyphase-responsive relaying element being such that said element does not respond to any zero-sequence component of said compensated polyphase voltages.

10. A protective-relaying combination for responding to certain faults on a three-phase transmission-line, including: a means, energized from the line-voltage at the relaying station, for producing a set of derived polyphase voltages having a phase-sequence corresponding to the line-voltages; a compensating-means, including a compensator connected in series with one of said derived voltages, and having substantially the same impedance- :angle as the line-impedance of said three-phase transmission-line, for producing a set of compensated polyphase voltages; a means for energizing said compensator proportionately to the line-current which flows in the corresponding line-conductor of the three-phase transmission-line; and a two-circuit polyphase-responsive relaying element, energized from two substantially quadrature-related phases from said compensated polyphase voltages.

11. A compensated-voltage relaying unit for responding to certain faults on a three-phase transmission-line, said unit including: a voltage-deriving means, energized from the line-voltage at the relaying station, for producing a set of derived polyphase voltages having a phase-sequence aerate-9 23 corresponding to the line-voltages; a set of three compensators, connected in series-circuit relation to the respective phases of said derived polyphase voltages, and energized proportionately to the respective line-currents in the corresponding line-wires of the transmission-line;

from the line-voltage at the relaying station, for producing a set of derived polyphase voltages having a phase- ;sequence corresponding to theline-voltages; a set of three line-drop compensators, connected in series-circuit relation to the respective phases of said derived polyphase voltages, and energized proportionately to the respective line-currentsin the corresponding line-wires of the transmission-line, each compensator having an impedance equivalent to theline-impedance to a predetermined faultlocation, whereby the compensated polyphase voltages collapse to a single phase upon the occurrence of a lineto-line fault across any pair of'line-phases at said predetermined fault-location, whereby the compensated polyphase voltages have a negative sequence of phases upon the occurrence of a line-to-line fault across any pair of line-phases between the relaying station and said predeterlrnined fault-location, and-whereby the compensated polyphase voltages have a positive sequence of phases upon the -occurrence of a line-to-line fault across any pair of line- .phases at any other fault-location; and a polyphaseresponsive relaying'element, energized from said compensated polyphase voltages, for controlling an electrical eircuitwhen the compensated polyphase voltages have a negative sequence of phases.

13. A compensated-voltage phase-fault relaying unit for responding to line-to-line faults which occur across any one of the three pairs of line-phases of a three-phase transmission-line, said unit including: a means, energized -=from the line-voltage at the relaying station, for producing a set of derived polyphase voltages having a phasesequence corresponding to the line-voltages; a set of three line-drop compensators, connected in series-circuit relation to the respective phases of said derived polyphase voltages, and energized proportionately to the respective line-currents in the corresponding line-wires of the transmission-line, each compensator having an impedance equivalent to the line-impedance to a predetermined faultlocation, whereby the compensated polyphase voltages collapse to a single phase upon the occurrence of a lineto-line fault across any pair of line-phases at said predetermined faultelocaticn, whereby the compensated poly phase voltages have a negative sequence of phases upon the occurrence or a linc-to-line fault across any pair line-phases between the relaying station and said predetermined fault-location, and whereby the compensated polyphase voltages have a positive sequence of phases npon the occurrence of a line-to-line fault across any ;pair of line-phases at any other fault-location; and a polyphase-responsive relaying element, energized from .said compensated polyphase voltages, for controlling an electrical circuit when the compensated polyphase voltages have a negative sequence of phases, the circuitconnections of said polyphase-responsive relaying element being such that said element does not respond to any zero-sequence component of the compensated polyphase voltages.

14. A compensated voltage phase-fault relaying unit for respo-nding to line-to-line faults which occur across any one of the three pairs of line-phasesof a three-phase.

transmission-line, said unit including: a means, energized from the line-voltage at the relaying station, for producing a set of derived polyphase voltages having a phasesequence corresponding to the line-voltages; a set of three line-drop compensato-rs, connected in series-circuitlrelw tionito the respective phases of said derived polyphase voltages, and energized proportionately to the respective line-currents in the corresponding line-wires of the transmissiondine, each compensator having an impedance equivalent to the line-impedance to a predetermined faultlocation, whereby the compensated polyphase voltages collapse to a single phase upon the occurrence of a lineto-line fault across any pair of line-phases at said predetermined fault-location, whereby the compensated polyphase voltages have a negative sequence of phases upon the occurrence of a line-to-line fault across any pair of line-phases between the relaying station and said predetermined fault-location, and. whereby the compensated polyphase voltages have a positive sequence of phases upon the occurrence of a line-to-line fault across any pair of line-phases at any other fault-location; and a torque-producing relaying element having a polyphase stationary element which is energized from said compensated polyphase voltages; and having a light-weight cylindrical rotor element of conducting material, carrying a contact which is moved in a responsive direction when the compensated polyphase voltages have a negative se quence of phases.

15. A compensated-voltage phase-fault relaying unit for responding to line-to-line faults which occur across any one of the three pairs of line-phases of athree-phase transmission-line, said unit including: a means, energized from the line-voltage at the relaying station, forproducing a set of derived polyphase voltages having a phasesequence corresponding to the line-voltages; a set of three line-drop compensators, connected in series-circuit relation to the respective phases of said derived polyphase voltages, and energized proportionately to the respective line-currents in the corresponding line-wires of thetransmission-line, each compensator having an impedance equivalent to the line-impedance to a predetermined faultlocation, whereby the compensated polyphase voltages collapse to a single phase upon the occurrence of a lineto-line fault across any pair of line-phases at said predetermined fault-location, whereby the compensated polyphase voltages having a negative sequence of, phases upon the occurrence of a line-to-line fault across any pair of iine-phases between the relaying station and said predetermined fault-location, and whereby the compensated polyphase voltages having a positive sequence of phases upon the occurrence of a line-to-line fauit across any pair of line-phases at any other fault-locations; and a polyphase-responsive torque-producing relayvoltages for producing two diametrically flowing fluxes, said relaying element further having a light-weight cylindrical rotor element of conducting material, carrying a contact which is moved in a responsive direction when the compensated polyphase voltages have a negative sequence of phases.

l6. A compensated-voltage phase-fault relaying unit for responding to line-to-line faults which occur across any one of the three pairs of line-phases of a threephase transmission-line, said unit including: a means, energized from the line-voltage at the relaying station, for producing a set of derived polyphase voltages having a phase-sequence corresponding to the line-voltages; a set of three line-drop compensators, connected in seriescircuit relation to the respective phases of said derived polyphase voltages, and energized proportionately to the respective line-currents in the corresponding jline-wires of the transmission-line, each compensator having an impedance equivalent to the line-impedance to apr edetermined fault-location, whereby the compensated poly- 'phase'voltages collapse to a single phase upon the occurrence of a line-to-line fault across any pair of linephases at said predetermined fault-location, whereby the compensated polyphase voltages have a negative sequence of phases upon the occurrence of a line-to-line fault across any pair of line-phases between the relaying station and said predetermined fault-location, and whereby the compensated polyphase voltages have a positive sequence of phases upon the occurrence of a line-to-line fault across any pair of line-phases at any other faultlocation; and a two-circuit polyphase-responsive relaying element, energized from said compensated polyphase voltages, for controlling an electrical circuit when the compensated polyphase voltages have a negative sequence of phases. l

17. A compensated-voltage phase-fault relaying unit for responding to line-to-line faults which occur across any one of the three pairs of line-phases of a threephase transmission-line, said unit including: a means, energized from the line-voltage at the relaying station. for producing a set of derived polyphase voltages having a phase-sequence corresponding to the line-voltages; a set of three line-drop compensators, connected in series circuit relation to the respective phases of said derived polyphase voltages, and energized proportionately to the respective line-currents in the corresponding line-wires of the transmission-line, each compensator having an impedance equivalent to the line-impedance to a predetermined fault-location, whereby the compensated polyphase voltages collapse to a single phase upon the occurrence of a line-to-line fault across any pair of linephases at said predetermined fault-location, whereby the compensated polyphase voltages having a negative sequence of phases upon the occurrence of a line-to-line fault across any pair of line-phases between the relaying station and said-predetermined fault-location, and whereby the compensated polyphase voltages having a positive sequence of phases upon the occurrence of a line-toline fault across any pair of line-phases at any other fault-location; and a two-circuit polyphase-responsive relaying element, energized from said compensated polyphase voltages, for controlling an electrical circuit when the compensated polyphase voltages have a negative sequence of phases, the circuit-connections of said polyphase-responsive relaying element being such that said element does not respond to any zero-sequence component of the compensated polyphase voltages.

18. A compensated-voltage phase-fault relaying unit for responding to line-to-line faults which occur across any one of the three pairs of line-phases of a threephase transmission-line, said unit including: a means, energized from the line-voltage at the relaying station, for producing a set of derived polyphase voltages having a phase-sequence corresponding to the line voltages; a set of three line-drop compensators, connected in seriescircuit relation to the respective phases of said derived polyphase voltages, and energized proportionately to the respective line-currents in the corresponding line-wires of the transmission-line, each compensator having an impedance equivalent to the line-impedance to a predetermined fault-location, whereby the compensated polyphase voltages collapse to a single phase upon the occurrence of a line-to-line fault across any pair of line-phases at saidpredeter mined fault-location, whereby the compensated polyphase voltages have a negative sequence of phases upon the occurrence of a line-to-line fault across any pair of line-phases between the relaying station and said predetermined fault-location, and whereby the compensated polyphase voltages have a positive sequence of phases upon the occurrence of a line-to-line fault across any pair of line-phases at any other faultlocation; and a two-circuit polyphase-responsive relaying element, energized from two substantially quadraturerelated phases from said compensated polyphase voltages,:for controlling an electrical circuit when the com- 26 pensated polyphase voltages have a negative sequence or phases.

19. A protective-relaying combination for protecting a three-phase transmission-line against all faults, involving more than one line-phase, which occur on the transmission-line between the relaying station and a predetermined fault-location on the line; said combination including a compensated-voltage phase-fault relaying unit including: a means, energized from the line-voltage at the relaying station, for producing a set of derived polyphase voltages having a phase-sequence corresponding to the line-voltages; a set of three line-drop compensators, connected in series-circuit relation to the respective phases of said derived polyphase voltages, and energized proportionately to the respective line-currents in the corresponding line-wires of the transmission-line, each compensator having an impedance equivalent to the line-impedance to a predetermined fault-location, whereby the compensated polyphase voltages collapse to a single phase upon the occurrence of a line-to-line fault across any pair of linephases at said predetermined fault-location, whereby the compensated polyphase voltages have a negative sequence of phases upon the occurrence of a line-to-line fault across any pair of line-phases between the relaying station and said predetermined fault-location, and whereby the compensated polyphase voltages have a positive sequence of phases upon the occurrence of a line-toline fault across any pair of line-phases at any other fault-location; and a polyphase-responsive relaying element, energized from said compensated polyphase voltages, for controlling an electrical circuit when the compensated polyphase voltages have a negative sequence of phases; in combination with a three-phase fault-responsive relaying means which responds to all other faults, involving more than one line-phase, which occur on the transmission line between the relaying station and substantially the same predetermined fault-location on the line; and a relaycontrolled circuit-means for performing a fault-protective function for the transmission-line, in response to either said phase-fault relaying unit or said three-phase fault-responsive relaying means.

20. A compensator relaying assembly, for responding to' all kinds of multiple-conductor faults on a threephase transmission-line, comprising two diverse compensated-voltage relaying-units, each having a polyphaseresponsive relaying element for controlling an electrical circuit when its impressed polyphase voltages have a negative succession of phases, said two relaying-units including a means, energized from the transmission-line at the relaying station, for providing a set of derived polyphase voltages having the same phase-sequence as the transmission-line, each of said relaying-units having a different compensator-assembly for energizing its polyphase-responsive relaying element from said derived polyphase voltages, each of the two different compensatorassemblies comprising one or more compensators which are serially connected to as many phases of the derived polyphase voltages to produce a set of compensated polyphase voltages, each compensator having an effective impedance having substantially the same impedanceangle as the transmission-line, and each compensator being energized proportionately to the line-current in the corresponding phase of the transmission-line, the two different compensator-assemblies being such that each relaying-unit responds to some, but not all, of the possible kinds of multiple-conductor faults on the transmission-line, out to the same predetermined balance point, but the two units together covering all kinds of such faults.

21. A protective-relaying combination for use in protecting a three-phase line-section against a line-to-line fault which may occur across any one of the three pairs of line-phases, said combination including: a means, energized from the line-voltage at the relaying station, for deriving a set of derived three-phase voltages for relaygarages ring purposes; a set of three line-drop compensators, connected in series relation to the respective phases of the derived three-phase voltages, for deriving a set of compensated three-phase relaying voltages which reproduce the line-voltages at some predetermined fault-location in the protected line-section, upon the occurrence of any line-to-line fault at that location; and a relaying means, energized from said compensated three-phase relaying voltages, for developing an operating force which is responsive to the magnitude of the negative-sequence component of said compensated three-phase relaying voltages, and a restraining force which is similarly responsive to the magnitude of the positive-sequence component of said compensated relaying voltages.

22. A protective-relaying combination for use in protecting a three-phase line-section against a line-to-iine fault which may occur across any one of three pairs'of line-phases, said combination including: a means, energized from the line-voltage at the relaying station, for deriving a set of derived three-phase voltages for relaying purposes; a set of three line-drop compensators, connected in series relation to the respective phases of the derived three-phase voltages, for deriving a set of compensated three-phase relaying voltages which reproduce the line-voltages at some predetermined fault-location in the protected line-section, upon the occurrence of any line-to-line fault at that location; and a relay operating on the principle of a polyphase induction motor, energized from said compensated three-phase relaying voltages.

23. A protective-relaying combination for use in protecting a three-phase line-section against a line-to-line fault which may occur across any one of the three pairs of line-phases, said combination including: a means, en-

ergized from the line-voltage at the relaying station, for

deriving a set of three derived three-phase. voltages for relaying purposes; a set of line-drop compensators, connected in series relation to the respective phases of the derived three-phase voltages, for deriving a set of compensated three-phase relaying voltages which reproduce the line-voltages at some predetermined fault-location in the protected line-section, upon the occurrence of any line-to-line fault at that location; and a relaying means, energized from two of the delta phases of said compensated three-phase relaying voltages, for operating in response to the product of the magnitudes of said two delta phases, multiplied by the sine of the phase-angle between them.

24. In a relaying assembly, a phase-sequence-responsive translating device having a plurality of first input terminals suitable for energization by a polyphase voltage, said device being responsive to the diflerence between the positive-phase-sequence component and the negativephase-sequence component of a polyphase voltage applied to the terminals for operation from a first circuitcontrol condition to a second circuit-control condition, a plurality of impedance units each having an impedance angle adjustable in the range of impedance angle of a line of a polyphase transmission system in a zone normally protected by distance relays, each of said impedance units having a terminal connected to a separate one of the first input terminals and having a second terminal, and a plurality of input means each effective when energized for directing a current through at least part of a separate one of the impedance units which does not pass through the translating device, whereby the translating means is energized by a polyphase voltage dependent on the resultant of the polyphase voltage applied to the second terminals and the voltage across the impedances.

25. In a relaying assembly, a phase-sequence-responsive, translating device having a plurality of first input terminals suitable for energization by a polyphase voltage, said device being responsive to the difference between the positive-phase-sequence component and the negativephase-sequence component of a polyphase voltage ap- 28 plied to the terminals for operation from a first-circuitcontrol condition to a second circuit-control condition, a plurality of impedance units each having an impedance angle adjustable in the range of impedance angle of a line of a polyphase transmission system in a zone nor- .mally protected by distance relays, each of said impedance units having a terminal connected to a separate one of the first input terminals and having a second terminal, and a plurality of input means each effective when energized for directing a current through at least part of a separate one of the impedance units which does not pass through the translating device, whereby the translating means is energized by a polyphase voltage dependent on the resultant of the polyphase voltage applied to the second terminals and the voltage across the impedances, each of said impedance units comprising an adjustable resistor and an adjustable inductive reactance device adjustable respectively within the range of line resistance and line reactance angular range normally encountered in protected zones of distance-protected conventional polyphase transmission lines.

26. In a relaying assembly for protecting a polyphase,

transmission line, a phase-sequence-responsive translating device having a plurality of first input terminals suitable for energization by a polyphase voltage, said'deyice being responsive to the difterpnce between the positive-. phase-sequence component and sequence component of a polyphase voltage applied to the terminals for operation from a first circuit-control condition to a second circuit-control condition, and impedance means energized from a first position of a polyphase transmission line for energizing the translating device in accordance with polyphase voltages at a second position of such transmission line, such positions being substantially displaced from each other.

27. A compensated-voltage relaying unit for responding to certain faults on a three-phase transmission-line,

.said unit including: a voltage-deriving means, energized sated polyphase voltages, for controlling an electrical circuit when the compensated polyphase voltages have a negative sequence of phases, each of said compensators including an inductive reactance element having a core provided with an airgap.

References Cited in the file of this patent UNITED STATES PATENTS 1,615,691 Fortescue et al. Jan. 25, 1927 1,752,947 Genkin Apr. 1, 1930 1,816,771 Grassot July 28, 1931 1,939,044 Evans Dec. 12, 1933 1,963,193 Evans June 19, 1934 2,221,602 Parsons Nov. 12, 1940 2,295,398 Griscom Sept. 8, 1942 2,354,152 Sonneman July 18, 1944 2,408,208 Goldsborough Sept. 24, 1946 2,426,062 Sonneman. Aug. 19, 1947 2,445,429 Goldsborough July 20, 1948 2,479,345 Goldsborough Aug. 16, 1949 2,743,396 Goldsborough Apr. 24, 1956 FOREIGN PATENTS 585,516 Great Britain Feb. 10, 1947 the negative-phase-